IE54117B1

IE54117B1 - Apparatus for recovering the kinetic energy of sea waves

Info

Publication number: IE54117B1
Application number: IE1711/82A
Authority: IE
Original assignee: Interproject Service Ab
Priority date: 1981-07-16
Filing date: 1982-07-15
Publication date: 1989-06-21
Also published as: IN158374B; EP0070817B1; DE3277421D1; IE821711L; NO154768C; EP0070817A3; US4773221A; NO822459L; AU551291B2; AU8604682A; NO154768B; EP0070817A2; SE8104407L; JPS5859381A; SE427131B

Abstract

Apparatus for recovering kinetic energy bound in the movement of water waves. The apparatus comprises a bouyant unit (2) and an energy-absorbing device connected to the bouyant unit. The energy-absorbing device comprises an immersed rigid piston (6) which is slideably arranged in a substantially vertical, elongate accelerating tube (1) which is intended to be immersed in the water and which is open at both ends thereof. The accelerating tube is connected to the bouyant unit (2) so as to accompany movement of the unit imparted thereto by the wave movement of the water. The working stroke (1) of the piston in the accelerating tube is limited by means of movement-limit means (8,9) incorporated in the accelerating tube and arranged to abrogate the force acting on the piston. In accordance with one suitable embodiment, these movement-limiting means comprise openings (9) arranged in the accelerating tube and co-acting with corresponding openings (8) in the piston (6).

Description

The present invention relates to apparatus for recovering kinetic energy bound in the movement of water waves, said apparatus including a buoyant unit and a device absorbing energy directly from the water constituted by an immersed rigid piston slideably arranged in a substantially vertical elongate accelerating tube which is intended to be immersed in said water and which is permanently open at both ends and connected to the buoyant unit so as to accompany the movement of said unit imparted thereto by said wave movement.

In known kinetic-energy recovering apparatus of this kind there is no limit to the extent of travel of the piston within the accelerating tube. Consequently, the piston or piston rod are liable to be damaged when subjected to excessive forces, for example when subjected to forces emanating from very rough or heavy seas. In those known cases where the piston is arranged in a widened portion of the accelerating tube, as is in the apparatus according to GB-A-2 029 907, there is the further risk of the piston striking the surfaces defining the bottom of this widened portion, when the sea is rough or heavy, resulting in damage to the piston or piston rod. In AU-B-55812/73 is set forth an apparatus comprising piston movement-damper means which however do not act to exactly limit or define the stroke of the piston in the tube. - 2 54117 An object of the present invention is to provide an apparatus for recovering the kinetic energy of water waves, having a piston which is arranged for movement within an accelerating tube and the extent of the movement of which piston is limited in such a manner that the force acting on the piston is greatly reduced when the piston reaches the limit positions of said extent of piston movement.

Accordingly, there is provided an apparatus having the characterizing features set forth in the accompanying claims.

According to one preferred embodiment of the invention the movement-limiting or pressure relief means comprise openings in the accelerating tube wall. Said openings should not be mixed up with the openings in the upper end of the tube according to GB-A-2 029 907 which serve to let in and let out water of the tube.

The invention will now be described in more detail with reference to exemplary embodiments illustrated schematically in the accompanying drawings, in which Figure 1 illustrates in perspective a first embodiment of an apparatus constructed in accordance with the invention, comprising a buoyant unit and an accelerating tube; Figure 2 is a longitudinal sectional view of that part of the apparatus shown in Figure 1 which incorporates the limit means for restricting the extent of piston travel and for abrogating the force acting on the piston; and Figure 3 is a longitudinal sectional view of a further embodiment of an accelerating tube in apparatus constructed in accordance with the invention, the Figure also showing that part of the accelerating tube which incorporates the piston-movement limiting means.

Figure 4 is a longitudinal sectional view of a still further embodiment of an accelerating tube in an apparatus constructed in accordance with the invention, the Figure showing that part of the accelerating tube which incorporates the piston-movement limiting means. - 3 The apparatus illustrated in Figure 1 comprises mainly an accelerating tube 1 and a buoyant unit 2. As illustrated, the apparatus is moored by means of mooring lines 3. The buoyancy of the buoyant unit 2 and the length of the accelerating tube 1 are such that the end 4 of the tube 1 lies beneath the surface of the water.

The maximum distance travelled by the piston 6 is shown in figure 2, by means of the double-headed arrow 5. The piston 6 is provided with openings 8 adjacent to its upper end 7. The accelerating tube 1 is provided with corresponding openings 9 in region of the lower end 10 of the piston 5. When the piston 5 is moved upwardly from the position illustrated in Figure 2, water is able to stream freely through the openings 9, thereby to equalize the forces acting on the piston and relieve the piston of said forces. This means that the position in which the piston is shown in Figure 2 constitutes the highest position to which the piston 6 can move in the tube 1. When the piston 5 moves downwardly the openings 8 in the cylindrical surface of the piston 6 will reach a position at which they are in register with the openings 9 in the tube 1. When this position is reached, the water pressure within the tube 1 and the water pressure externally of said tube will be equalized, thereby relieving the load on the piston 6. This constitutes the lowermost position to which the piston of the embodiment illustrated in Figure 2 can move. Thus, the length of stroke of the piston is limited to the highest level L according to Figure 2, irrespective of the height of the waves.

In the Figure 3 embodiment, the length of stroke M of a piston 11 is restricted by an upper and a lower widening 12 and 13 respectively, arranged in the accelerating tube 14. When the piston 11 reaches a position, during its upward movement, at which it is accommodated in the widening 12 the water releases its pressure against the underside of the piston and rushes past the piston, into the space between the outer cylindrical surface of the piston 11 and the wall defining said widening 12. This causes the piston 11 to remain in said position. Correspondingly, when moving downwardly the piston 11 will reach a position in which it is accommodated in the lower widening 13, and will remain in this position due to the equalization of forces acting on the top and bottom working surfaces of the piston. Thus, the working - 4 54117 stroke of the piston is restricted to the distance M, irrespective of the height of the waves or the roughness of the sea.

In the figure 4 embodiment, the length of stroke N of a piston 15 is restricted to the length of a cylindrical insert 16 which is arranged coaxially inside tube 17. Insert 16 is attached to tube 17 via an upper and a lower ring 18 and 19 respectively. Between insert 16 and tube 17 there is a filling 20. When piston 15 reaches a position outside the insert 16 piston 15 is guided by guides 21 and 22 until water releases its pressure against the piston substantially in the manner described with reference to Figure 3.

Claims

1. Apparatus for recovering kinetic energy bound in the movement of water waves, said apparatus including a buoyant unit and a device 5 absorbing energy directly from the water constituted by an immersed rigid piston slideably arranged in a substantially vertical elongate accelerating tube which is intended to be immersed in said water and which is permanently open at both ends and connected to the buoyant unit so as to accompany the movement of said unit imparted thereto by 10 said wave movement, wherein the maximum working stroke of the piston in the accelerating tube is defined by pressure relief means arranged on the accelerating tube at least below the middle position of the piston and laterally of that piston. 15

2. Apparatus according to claim 1, wherein the pressure relief means comprise at least one opening in the accelerating tube arranged to co-act with at least one corresponding opening in the piston.

3. An apparatus according to claim 1, wherein said pressure relief 20 means comprise at least one widened portion in the accelerating tube,

4. An apparatus according to claim 1, wherein said pressure relief means comprise at least one tubular insert arranged coaxially inside the accelerating tube.

5. Apparatus for recovering kinetic energy bound in the movement of water waves, substantially as described herein with reference to and as shown in Figures 1 and 2 or Figure 3 or Figure 4 of the accompanying drawings.